[0001] The present invention relates to a brushless DC motor, and more particularly to a
brushless DC motor which does not employ a special position detecting means to obtain
a rotating position signal for switching an excited phase during a normal rotation.
[0002] Brushless DC motors have been used in video tape recorders (VTRs) for driving the
rotary head. In the conventional brushless DC motor for driving the rotary head of
VTR, since the excited phase of stator coils is switched according to the rotation
of the rotor, a plurality of special position detecting elements such as Hall elements
are provided to detect a rotor position, and furthermore, another position detecting
means is provided to detect a standard rotating position of the rotor so that the
rotary head mounted on the rotor can scan specified positions on a magnetic tape.
However, use of such position detecting means is one of the obstacles to reduce cost
and size of the motor.
[0003] Therefore, some brushless DC motors which do not use the position detecting means
have been proposed. In these brushless DC motors, some processes are provided to obtain
the rotating position signal for switching the excited phase of the stator coils by
detecting the counter electromotive forces generated in the stator coils. Since the
counter electromotive force is used to obtain the rotating position signal, the rotating
position signal cannot be obtained when the rotor is not rotating. Therefore, when
starting the motor, a specific stator coil is energized for positioning the rotor
thereby to detect a starting position. This technique is disclosed, for example, in
the Japanese Laid-Open Patent Application No. 55-160980 and in the German Patent DE-A-2428718.
[0004] However, in such brushless DC motors, when positioning the rotor at starting, certain
time is required until the permanent magnet rotor comes to a standstill at a desired
position because the rotor vibrates about the desired position. The time required
for the permanent magnet rotor to become stationary varies considerably with the load
or the inertia of the rotor, and is fairly long particularly when the inertia of the
rotor is large. Furthermore, if the rotor is in a position apart by 180% from the
desired position where the rotor is to be positioned, the rotor cannot rotate unless
no disturbance is caused, resulting in failure of starting.
[0005] Another method of starting a DC motor is disclosed in FR-A-2524729 wherein a method
is described which involves using an oscillator for generating a pulse signal. This
is used to sequentially energise the stator coils in order to start the motor.
[0006] An object of the present invention is to provide a brushless DC motor which can be
positively started by using only one position detecting element.
[0007] Another object of the present invention is to provide a brushless DC motor which
is capable of producing a reference position signal which is used in an apparatus
(such as VTR) in which the motor is equipped.
[0008] The brushless DC motor according to the present invention energizes forcibly and
sequentially a plurality of stator coils at a starting time to start the permanent
magnet rotor. When a phase switching position for a specific stator coil is detected
by the single position detecting element (such as Hall element), the specific stator
coil is energized, and, from this point, counter electromotive forces generated in
stator coils begin to be detected to obtain rotating position signals so that the
stator coils are thereafter energized in response to the rotating position signals.
[0009] In one full rotation (i.e. 360°) of the rotor, the position detecting element generates
a plurality of position signals as pulse signals having the same pulse width for indicating
positions (phase switching positions) where each specific stator coil should be energized.
It is preferable, however, to construct the motor so that the position detecting element
does not generate one of the plurality of position signals or that the position detecting
element generates as one of the plurality of position signals, a signal which has
a pulse width narrower than that of the other of the plurality of position signals.
If constructed in this manner, the position where the position signal is missed or
the position signal has a narrower pulse width can be identified by logically processing
the plurality of position signals thereby to obtain a reference position signal in
each full rotation of the rotor.
[0010] It is further preferable to reduce electromagnetic noise by reducing a driving current
at each switching on of the excited phase when forcibly energizing a plurality of
stator coils sequentially at starting so that driving transistors operate within their
safe operating ranges.
[0011] The brushless DC Motor according to the present invention comprises a permanent magnet
rotor magnetized to have 2n poles (n is a positive integer); a plurality of stator
coils (2a, 2b, 2c) mounted on a stator; a coil driving circuit for energizing said
plurality of stator coils; a position detecting means composed for detecting at least
one specific rotating position of said rotor; a starting circuit; a position detecting
arithmetic circuit for obtaining a rotating position signal of said permanent magnet
rotor by processing a counter electromotive force generated in each of said plurality
of stator coils; and a switching means for switching between a starting circuit configuration
and a normal running circuit configuration; characterized in that: said starting circuit
comprises an oscillator for generating a pulse signal which, in said starting circuit
configuration, is applied to said coil driving circuit to forcibly and sequentially
energize said plurality of stator coils; said switching means is a driving status
switching circuit which switches said coil driving circuit from being responsive to
an output signal of said starting circuit in said starting circuit configuration to
being responsive to an output signal of said position detecting circuit in said normal
running circuit configuration exclusively when the position detecting means detects
a rotating position of the rotor corresponding to a rotating position signal according
to which a specific predetermined one of said plurality of stator coils is to be energized.
[0012] The above and other objects, features and advantages of the invention will be apparent
from the following description taken in connection with the accompanying drawings
in which:
[0013] Fig. 1 is a circuit diagram showing an embodiment of brushless DC motor according
to the present invention;
[0014] Fig. 2 is a waveform chart to explain a position detecting arithmetic circuit used
in the motor shown in Fig. 1;
[0015] Fig. 3 is a waveform chart to explain phases of rotating positions to be detected
by a position detecting means used in the motor shown in Fig. 1;
[0016] Fig. 4 is an illustrative chart showing some magnetized patterns of a permanent magnet
rotor used in the motor shown in Fig. 1;
[0017] Fig.5 is a waveform chart to explain a pulse signal generating circuit and a reference
position detecting circuit used in the motor shown in Fig. 1;
[0018] Fig. 6 is a waveform chart to explain a starting circuit and a driving current control
circuit used in the motor shown in Fig. 1.
[0019] For the purpose of an explanation, an example using a permanent magnet rotor magnetized
to have six poles (n = 3) will be described but it should be noted that the rotor
is not limited to one referred to herein.
[0020] Referring to Fig. 1, 1 is a permanent magnet rotor having six poles, in which each
N pole has a specific shape at a portion on the inner circumference of the rotor to
be detected by a position detecting element to obtain a rotating position of the rotor,
which will be described in detail later. Needless to say, the magnetization for the
detection of the rotating position is not limited only to the portion on the inner
circumference of the permanent magnet rotor 1.
[0021] Reference numbers 2a, 2b and 2c are stator coils.
[0022] Reference number 6 is a coil driving circuit connected at input terminals 7a, 7b
and 7c respectively with common terminals of switches 18a, 18b and 18c constituting
a driving status switching circuit 18, and at output terminals 8a, 8b and 8c respectively
with the stator coils 2a, 2b and 2c.
[0023] The coil driving circuit 6 is responsive to the largest one of the input voltages
applied to the input terminals 7a, 7b and 7c. The coil driving circuit 6 energizes,
when a voltage at 7a is the largest, the stator coil 2a via 8a; when a voltage at
7b is the largest, the stator coil 2b via 8b; and when a voltage at 7c is the largest,
the stator coil 2c via 8c. The circuit 6 is composed, for example, of driving transistors
40a, 40b and 40c as shown in Fig. 1.
[0024] Reference numeral 16 is a starting circuit which generates periodically repeating
signals at output terminals 17a, 17b and 17c which are respectively connected to the
input terminals 7a, 7b and 7c of the coil driving circuit 6 via the change-over switches
18a, 18b and 18c of the switching circuit 18 at starting, thereby to forcibly energize
the stator coils 2a, 2b and 2c sequentially.
[0025] Reference numeral 41 is a triangular wave oscillator to generate triangular wave
signals, 42 is a pulse signal generator to generate pulse signals synchronized with
the triangular wave signals from the triangular wave oscillator 41, 47 is a divider
to divide the pulse signals from the pulse signal generator 42, and 43 is a distributor
to distribute the divided pulse signals from the divider 47.
[0026] Reference numeral 21 is a position detecting arithmetic circuit which processes counter
electromotive forces generated in the stator coils 2a, 2b and 2c to obtain rotating
position signals of the permanent magnet rotor 1, and is connected to the input terminals
7a, 7b and 7c of the coil driving circuit 6 via the change-over switches 18a, 18b
and 18c of the switching circuit 18 during the steady-state rotation of the rotor
for sequentially energizing the stator coils 2a, 2b and 2c. Reference numerals 3a,
3b and 3c are rectifying circuits to respectively extract non-energized areas (upper
area greater than a power supply voltage +Vcc, in this case) of the counter electromotive
forces generated in the stator coils 2a, 2b and 2c. Reference numerals 4a, 4b and
4c are discharge-type voltage-current conversion circuits which respectively convert
half waveform counter electromotive forces obtained respectively by the rectifying
circuits 3a, 3b and 3c into currents, 5a, 5b and 5c are attraction-type voltage-current
conversion circuits which respectively convert the half waveform counter electromotive
forces obtain respectively by the rectifying circuits 3a, 3b and 3c into currents,
and 11a, 11b and 11c are integrating capacitors which are charged respectively by
the voltage-current conversion circuits 4b, 4c and 4a, and discharged respectively
by the voltage-current conversion circuits 5c, and 5a and 5b. A bias power source
12 provides a proper DC bias voltage.
[0027] Reference numeral 50 is an initial value setting circuit, in which DC power sources
10a, 10b and 10c respectively provide voltages Ea, Eb and Ec, as initial values, for
the integrating capacitors 11a, 11b and 11c through transfer switches 9a, 9b and 9c
of a switching circuit 9 at starting. Here, voltage Ec is set greater than voltages
Ea and Eb.
[0028] Hereinafter, a status wherein the stator coils 2a, 2b and 2c are driven by the output
signals of the starting circuit 16 will be called an "externally synchronized status",
and a status wherein the stator coils 2a, 2b and 2c are driven by the output signals
of the position detecting arithmetic circuit 21 will be called a "position detecting
status".
[0029] Each energized phase in the externally synchronized status is the same as that of
a synchronous motor and is different from that of a DC motor, namely, the energized
phase in the position detecting status. In other words, in the externally synchronized
status, the current is supplied partly even to the non-energized area of the counter
electromotive force waveform used to obtain the rotating position signals in the position
detecting status. Therefore, without proper measures, it is extremely difficult to
change from the externally synchronized status to the position detecting status.
[0030] Reference numeral 19 is a position detecting element such as a Hall element. The
position detecting element 19 is disposed opposed to the inner circumference of the
permanent magnet rotor 1 to detect positions corresponding to the phases of rotating
position signals for energizing a specific stator coil (here, the stator coil 2c).
[0031] Reference numeral 39 is a waveform shaping circuit to shape the waveform of an output
signal of the position detecting element 19, and may comprises a comparator for example.
[0032] Reference numeral 20 is a switching signal generating circuit which is responsive
to the output signal of the position detecting element 19 to generate a driving status
switching signal which is applied to the switching circuits 9 and 18 for switching
the status of the motor from the externally synchronized status to the position detecting
status.
[0033] Reference numeral 46 is a driving current control circuit which may be a constant
current source for example, and is connected in common with the emitters of the driving
transistors 40a, 40b and 40c to control the driving current.
[0034] In the externally synchronized status at starting, the transfer switches 9a, 9b and
9c are closed so that initial values Ea, Eb and Ec are transferred to the integrating
capacitors 11a, 11b and 11c, and the change-over switches 18a, 18b and 18c are in
the state turned to the output terminals 17a, 17b and 17c of the starting circuit
so that the stator coils 2a, 2b and 2c are forcibly and sequentially energized to
rotate the permanent magnet rotor 1. When the position detecting element 19 detects
a rotating position of the rotor 1 corresponding to rotating position signal according
to which the stator coil 2c is to be energized and generates a position signal, the
switching signal generating circuit 20 responsive to the position signal generates
a driving status switching signal which may be a differential of the position signal.
Then, the transfer switches 9a, 9b and 9c are opened in response to the driving status
switching signal, and the change-over switches 18a, 18b and 18c are changed over respectively
to the integrating capacitors 11a, 11b and 11c in response to the driving status switching
signal. Since the initial values Ea, Eb and Ec are given to the integrating capacitors
11a, 11b and 11c and Ec is greater than Ea and Eb, the coil driving circuit 6 supplies
a driving current through the output terminal 8c to the stator coil 2c.
[0035] As the result, the permanent magnet rotor 1 is accelerated in the position detecting
status, in which the position detecting arithmetic circuit 21 detects counter electromotive
forces of the stator coils and produces rotating position signals, and the coil driving
circuit 6 sequentially energizes the stator coils 2a, 2b and 2c according to the rotation
position signals, so that the rotor 1 continues to rotate.
[0036] Now, the position detecting arithmetic circuit 21 will be explained in detail with
reference to Fig. 2.
[0037] In Fig. 2 (a), 14a, 14b and 14c respectively represent voltages across the stator
coils 2a, 2b and 2c during the steady-state rotation. In each of these, the portions
above the +Vcc level are the waveform of the counter electromotive force generated
in the respective stator coil by the rotation of the permanent magnet rotor, while
in the portions below the +Vcc level the voltage drop caused by the coil driving current
and coil resistance is observed (shaded portion) in addition to the counter electromotive
force.
[0038] Fig. 2 (b) shows a voltage waveform at the integrating capacitor 11a, which becomes
a rotating position signal for driving the stator coil 2a. The position signal shown
in Fig. 2 (b) is obtained as follows by the position detecting arithmetic circuit
21.
[0039] That is, in Fig. 1, the voltage 14b of the stator coil 2b is rectified by the rectifying
circuit 3b to be a half-wave voltage which is the portion above the +Vcc. The half-wave
voltage is converted into a current by the voltage-current conversion circuit 4b to
charge the integrating capacitor 11a. Further, the voltage 14c of the stator coil
2c is rectified by the rectifying circuit 3C to be a half-wave voltage above the +Vcc
level, and then converted into a current by the voltage-current conversion circuit
5c to thereby discharge the integrating capacitor 11a. Thus, the voltage waveform
as shown in Fig. 2 (b) is obtained.
[0040] Likewise, Fig. 2 (c) shows a voltage waveform at the integrating capacitor 11b, which
becomes a rotating position signal for driving the stator coil 2b. Fig. 2 (d) shows
a voltage waveform at the integrating capacitor 11c, which becomes a rotating position
signal for driving the stator coil 2c. Fig. 2 (e) shows currents flowing through the
stator coils 2a, 2b and 2c according to the position signals respectively shown in
(b), (c) and (d) in Fig. 2, and 15a, 15b and 15c respectively show the currents flowing
through the stator coils 2a, 2b and 2c.
[0041] Next, phases of the rotating positions detected by the position detecting element
19 will be explained in detail with reference to Fig. 3 and Fig. 4.
[0042] Fig. 3 (a) shows the waveforms of the counter electromotive forces generated in the
stator coils when the brushless DC motor is rotating at a constant speed, wherein
29a, 29b and 29c show the counter electromotive forces respectively of the stator
coils 2a, 2b and 2c. T represents a period in which the permanent magnet rotor 1 makes
one mechanical rotation.
[0043] Fig. 3 (b), (c), (d) and (e) represent signal waveforms obtained by shaping waveforms
of the output signals of the position detecting element 19 with respect to respective
cases of the magnetized patterns of the rotor 1 which are shown in Fig. 4 (a), (b),
(c) and (d), respectively.
[0044] The position detecting element 19 detects positions corresponding to the phases of
the rotating position signals for the stator coil 2c. The positions corresponding
to the phases of the rotating position signals for the stator coil 2c are ϑ1, ϑ2 and
ϑ3 shown in the Fig. 3. Apparatuses such as VTRs using motors often require a reference
position signal indicating a reference position of a rotation of the motor for controlling
the motor operation. From the view point of obtaining the reference position signal
by using a single position detecting element, the position detecting element should
detect only one of the positions ϑ1, ϑ2 and ϑ3 as shown in Fig. 3 (b). On the other
hand, from the viewpoint of the starting characteristic of the motor, it is desirable
that the position detecting element detects all of the three positions ϑ1, ϑ2 and
ϑ3 as shown in Fig. 3 (c).
[0045] Therefore, to meet the above two exclusive requirements, such method can be adopted
that two of the three positions ϑ1, ϑ2 and ϑ3 are detected by the position detecting
means 19 with the normal width, and the remaining one position is not detected as
shown in Fig. 3 (d) or is detected with a width narrower than the normal width as
shown in Fig. 3 (e). In the case of Fig. 3 (d), the narrower width means that the
pulse ends before a time (point A in Fig. 3 (a)) where the voltage 29a changes from
the higher level than the +Vcc level to the lower level. The reference position signal
can be obtained by logically processing the signal shown in Fig. 3 (d) or (e) generated
by the position detecting element 19.
[0046] Fig. 4 (a), (b), (c) and (d) show magnetization patterns of the permanent magnet
rotor 1 for detecting positions corresponding to those shown in Fig. 3 (b), (c), (d)
and (e), respectively. The position detecting element 19 is provided at a suitable
position opposing the inner circumference of the rotor 1. The pulse signals having
the phases as shown in Fig. 3 (b), (c), (d) and (e) can be obtained by passing the
output signal of the position detecting element 19 through the waveform shaping circuit
39.
[0047] Referring again to Fig. 1, 22 is a pulse signal generating circuit which detects
at least one of the counter electromotive forces generated in the stator coils (stator
coils 2a, 2c here), and produces pulse signals, where 23a and 23c are input terminals
and 24 is an output terminal.
[0048] Reference numeral 25 is a reference position detecting circuit which is applied at
an input terminal 26 with the output pulse signals of the pulse signal generating
circuit 22 and at an input terminal 27 with the output signal of the waveform shaping
circuit 39, and logically processes these input signals to produce the reference position
signal in each full rotation of the permanent magnet rotor 1 at an output terminal
28.
[0049] In the pulse signal generating circuit 22, a comparator 32 is applied at its inverting
input terminal with the counter electromotive force generated in the stator coil 2a
and at its non-inverting input terminal with a reference voltage (+Vcc in this case),
and generates a pulse signal at an output terminal 38 when the voltage applied to
the inverting input terminal exceeds the +Vcc level. A comparator 33 is applied at
its inverting input terminal with the counter electromotive force generated in the
stator coil 2c and at its non-inverting input terminal with the reference voltage
(+Vcc in this case), and generates a pulse signal at an output terminal 30 when voltage
applied to the inverting input terminal exceeds the +Vcc level. A RS flip-flop 37
applied at its set (S) and reset (R) terminals with the output pulses of the comparators
32 and 33 respectively produces a pulse signal at its Q terminal. A D flip-flop 36
is applied at its clock input terminal (CK) with the output pulse of the pulse signal
generating circuit 22 and at its D input terminal with the output pulse of the waveform
shaping circuit 39, and outputs the D input status from its Q output terminal in response
to the pulse signal applied to the clock input terminal, thereby to obtain the reference
position signal per rotation of the permanent magnet rotor 1.
[0050] Now, this operation will be explained with reference to Fig. 5. Fig. 5 (a) shows
the waveforms of the counter electromotive forces 29a, 29b and 29c generated in the
stator coils 2a, 2b and 2c, which are the same as those shown in Fig. 3 (a). Fig.
5 (b) is the result of processing the waveform of the counter electromotive force
29a generated in the stator coil 2a at the output terminal 38 of the comparator 32.
Likewise, Fig. 5 (c) is the result of processing the waveform of the counter electromotive
force 29c generated in the stator coil 2c at the output terminal 30 of the comparator
33. By applying the pulse waveforms shown in (b) and (c) respectively to the set and
reset input terminals of the RS flip-flop 37, a pulse waveform shown in Fig. 5 (d)
is obtained at the terminal 24 in Fig. 1. Fig. 5 (e) is the output waveform of the
circuit 39 after shaping the output waveform of the position detecting element 19,
which is quite the same as that shown in Fig. 3 (e). If the hatched pulse does not
exist, such waveform is one shown in Fig. 3 (d).
[0051] Fig. 5 (f) shows a waveform at the Q output terminal of the D flip-flop 36. Since
the waveform (Fig. 5 (e)) after shaping the output waveform of the position detecting
element 19 is applied to the D input terminal (27) of the D flip-flop 36, and the
Q output (Fig. 5 (d)) of the RS flip-flop 37 is applied to the clock input terminal
(26) of the D flip-flop 36, the signal of Fig. 5 (f) is apparently obtained from the
Q output terminal (28) of the D flip-flop 36. The signal of Fig. (f) is the signal
appearing once per each full rotation of the permanent magnet rotor 1 and thus can
be used as the reference position signal. The frequency of output signal of the pulse
signal generating circuit 22 changes according to the number of rotations the permanent
magnet rotor 1, and thus can be used also as a signal for detecting the number of
rotations of the motor.
[0052] In Fig. 1, the starting circuit 16 sequentially turns on and off the driving transistors
40a, 40b and 40c by the annularly repeating signals to thereby energize forcibly the
stator coils 2a, 2b and 2c in sequence. However, since the stator coil, viewed from
the driving transistors, is an inductive load, the sudden change of the current of
the driving transistor turning from on to off state causes a high voltage appearing
between the emitter and collector of the driving transistor, which would damage the
driving transistor. Furthermore, the sudden change in the driving current would cause
vibration of the motor and electromagnetic noises.
[0053] Reference numeral 48 is a driving current instruction circuit which is responsive
to the output signal of the switching signal generating circuit 20 and output signals
(described below) of the starting circuit 16, and instructs the driving current control
circuit 46 to suppress the driving current energized phase at the switching timings
in the externally synchronized status.
[0054] Referring to Fig. 6, (a) shows an output signal of a triangular wave oscillator 41;
(b) show an output signal of a pulse signal generator 42 obtained from the signal
(a); (c) is an output signal of a divider 47 obtained by dividing the signal (b) (1/2
division, here); and (d), (e) and (f) are distributed output signals of a divider
47 obtained from the signal (c) and respectively applied to the bases of the driving
transistors 4a, 4b and 4c to thereby energize the stator coils 2a, 2b and 2c sequentially.
[0055] In the driving current instruction circuit 48, a signal shown in Fig. 6 (g) is obtained
by applying the signals of Fig. 6 (b) and (c) to an exclusive (EX)-OR gate circuit.
The phase in the "Low" level part of the signal (g) agrees with the timing to switch
the excited phase. The signal (g) is modulated by the triangular signal (a) to be
an instruction signal as shown in Fig. 6 (h). The driving current control circuit
46 is responsive to this instruction signal so as to supply driving currents as shown
in Fig. 6 (i), (j) and (k) respectively to the stator coils 2a, 2b and 2c.
[0056] That is, the current flowing through each stator coil during the switching timing
of the energized phase changes smoothly to suppress the generation of transient spike
voltage caused by the inductance of the stator coil.
[0057] Furthermore, 49 is the initially excited phase selection circuit which, when the
motor is stopped and the position detecting element 19 is detecting the position corresponding
to the rotating position signal for exciting to the stator coil 2c, controls the starting
circuit 16 to energize the stator coil 2c in the externally synchronized status, and,
when the position detecting means 19 is not detecting the position corresponding to
the rotating position signal for exciting the stator coil 2c, controls the starting
circuit 16 to energize the other stator coil than the stator coil 2c. For example,
the distributor 43 may be composed of a ring counter using flip-flops. It is easily
possible to set the initial condition of the ring counter by inputting a proper signal
into the set and reset input terminals of the ring counter depending on whether the
position detecting element 19 is or is not detecting the position signal at the starting
timing of the motor.
1. A brushless DC motor comprising:
a permanent magnet rotor (1) magnetized to have 2n poles (n is a positive integer);
a plurality of stator coils (2a, 2b, 2c) mounted on a stator;
a coil driving circuit (6) for energizing said plurality of stator coils;
a position detecting means (19) composed for detecting at least one specific rotating
position of said rotor;
a starting circuit (16);
a position detecting arithmetic circuit (21) for obtaining a rotating position signal
of said permanent magnet rotor (1) by processing a counter electromotive force generated
in each of said plurality of stator coils; and
a switching means (20) for switching between a starting circuit configuration and
a normal running circuit configuration;
characterized in that:
said starting circuit (16) comprises an oscillator (41) for generating a pulse signal
which, in said starting circuit configuration, is applied to said coil driving circuit
(6) to forcibly and sequentially energize said plurality of stator coils;
said switching means is a driving status switching circuit (20) which switches said
coil driving circuit (6) from being responsive to an output signal of said starting
circuit (16) in said starting circuit configuration to being responsive to an output
signal of said position detecting circuit (21) in said normal running circuit configuration
exclusively when the position detecting means (19) detects a rotating position of
the rotor corresponding to a rotating position signal according to which a specific
predetermined one of said plurality of stator coils is to be energized.
2. A brushless DC motor according to claim 1, wherein said position detecting arithmetic
circuit (21) comprises a rectifying circuit (3) which takes out whole or a part of
non-energised area of said counter electromotive force, a discharge-type voltage-current
conversion circuit (4) which converts an signal of said rectifying circuit into a
current, an attraction-type voltage-current conversion circuit (5) which converts
the output of said rectifying circuit into a further current, and an integrating capacitor
(11) which is charged and discharged by said discharge-type voltage-current conversion
circuit (4) and said attraction-type voltage-current conversion circuit (5).
3. A brushless DC motor according to claim 1 or 2, further comprising an initial value
setting circuit (50) for giving an initial value to said position detecting arithmetic
circuit (21) at the starting of said motor.
4. A brushless DC motor according to claim 1, 2 or 3, wherein said starting circuit (16)
comprises a triangular wave oscillator (41) for generating a triangular wave signal,
a pulse signal generator (42) for generating a pulse signal from said triangular wave
signal, a frequency divider (47) for dividing the frequency of the pulse signal from
said pulse signal generator (42), and a distributor (43) for obtaining from the frequency
divided pulse signal distributed signals which are applied to said coil driving circuit
(6) to sequentially energise said plurality of stator coils.
5. A brushless DC motor according to any one of the preceding claims, further comprising
a driving current control circuit (48) to suppress driving current supplied by said
coil driving circuit (6) to said plurality of stator coils when the coil driving circuit
(6) changes the excited coil from one to another.
6. A brushless DC motor according to any one of the preceding claims, further comprising
an initially excited phase selection circuit (49) which, when said permanent magnet
rotor (1) is stopped and said position detecting means (19) is detecting a specific
position at which a specific one (2c) of said plurality of stator coils (2a, 2b,2c)
is to be energised, controls said starting circuit (16) to energise said specific
one, and when said position detecting means (19) is not detecting said specific position,
controls said starting circuit (16) to energise another of said plurality of stator
coils different from said specific one.
7. A brushless DC motor according to any one of the preceding claims, wherein said position
detecting means (19) is so composed as to produce, in each full rotation of said stator,
n-1 position signals having the same signal width and one position signal having a
signal width narrower than that of the n-1 position signals or having no signal width,
and wherein said motor further comprises a reference position detecting means (25)
which logically processes said position signals to obtain a reference position signal
substantially corresponding to said one position signal.
8. A brushless DC motor according to claim 7, further comprising;
a pulse signal generating circuit (22) to obtain n pulse signals in each full rotation
of said rotor from the counter electromotive force generated in at least one of said
plurality of stator coils; and wherein
the reference position detecting means (25) produces a reference position signal per
rotation of said permanent magnet rotor (1) by logically processing said n pulse signals
from said pulse signal generating circuit (22) and said n position signals from said
position detecting means (19).
1. Moteur autosynchrone à courant continu comprenant :
un rotor (1) à aimant permanent aimanté afin qu'il possède 2n pôles (n étant un nombre
entier positif),
plusieurs bobinages de stator (2a, 2b, 2c) montés sur un stator,
un circuit (6) de pilotage de bobinages destiné à exciter les bobinages de stator,
un dispositif (19) de détection de position composé afin qu'il détecte au moins une
position particulière en rotation du rotor,
un circuit de démarrage (16),
un circuit arithmétique (21) de détection de position destiné à obtenir un signal
de position en rotation du rotor (1) à aimant permanent par traitement d'une force
contre-électromotrice créée dans chacun des bobinages de stator, et
un dispositif (20) de commutation entre une configuration de circuit de démarrage
et une configuration de circuit de fonctionnement normal,
caractérisé en ce que
le circuit de démarrage (16) comporte un oscillateur (41) à destiné à créer un signal
pulsé qui, dans la configuration du circuit de démarrage, est appliqué au circuit
(6) de pilotage de bobinages afin qu'il excite de manière forcée et successive les
bobinages de stator, et
le dispositif de commutation est un circuit (20) de commutation d'état de pilotage
qui commute le circuit (6) de pilotage de bobinages d'un état de sensibilité au signal
de sortie du circuit de démarrage (16) dans la configuration de circuit de démarrage
à la sensibilité à un signal de sortie du circuit (21) de détection de position dans
la configuration du circuit de fonctionnement normal exclusivement lorsque le dispositif
(19) de détection de position détecte une position du rotor en rotation qui correspond
à un signal de position en rotation pour lequel un bobinage prédéterminé particulier
parmi les bobinages de stator doit être excité.
2. Moteur autosynchrone à courant continu selon la revendication 1, dans lequel le circuit
arithmétique (21) de détection de position comprend un circuit redresseur (3) qui
prélève la totalité ou une partie de la zone non excitée de la force contre-électromotrice,
un circuit de conversion tension-courant (4) du type à décharge qui transforme un
signal du circuit redresseur en un courant, un circuit de conversion tension-courant
(5) du type à attraction qui transforme le signal de sortie du circuit redresseur
en un autre courant, et un condensateur d'intégration (11) qui est chargé et déchargé
par la circuit de conversion (4) du type à décharge et le circuit de conversion (5)
du type à attraction.
3. Moteur autosynchrone à courant continu selon la revendication 1 ou 2, comprenant en
outre un circuit (50) de consigne destiné à donner une valeur initiale au circuit
arithmétique (21) de détection de position lors du démarrage du moteur.
4. Moteur autosynchrone à courant continu selon la revendication 1, 2 ou 3, dans lequel
le circuit de démarrage (16) comporte un oscillateur (41) à ondes triangulaires destiné
à créer un signal sous forme d'une onde triangulaire, un générateur (42) destiné à
créer un signal pulsé à partir du signal à ondes triangulaires, un diviseur (47) de
la fréquence du signal pulsé provenant du générateur (42) de signaux pulsés, et un
distributeur (43) destiné à tirer du signal pulsé divisé en fréquence des signaux
distribués qui sont appliqués au circuit (6) de pilotage de bobinages afin que les
bobinages de stator soient excités successivement.
5. Moteur autosynchrone à courant continu selon l'une quelconque des revendications précédentes,
comprenant en outre un circuit (48) de réglage de courant de pilotage destiné à supprimer
le courant de pilotage transmis par le circuit (6) de pilotage de bobinages à plusieurs
bobinages de stator lorsque le circuit (6) de pilotage de bobinages passe d'un bobinage
excité à un autre.
6. Moteur autosynchrone à courant continu selon l'une quelconque des revendications précédentes,
comprenant en outre un circuit initialement excité (49) de sélection de phases qui,
lorsque le rotor à aimant permanent (1) est arrêté et le dispositif de détection de
position (19) détecte une position particulière pour laquelle un bobinage particulier
(2c) des bobinages de stator (2a, 2b, 2c) doit être excité, commande le circuit de
démarrage (16) afin qu'il excite le bobinage particulier et, lorsque le dispositif
(19) de détection de position ne détecte pas la position particulière, commande le
circuit de démarrage (16) afin qu'il excite un bobinage de stator autre que le bobinage
particulier.
7. Moteur autosynchrone à courant continu selon l'une quelconque des revendications précédentes,
dans lequel le dispositif (19) de détection de position est réalisé de manière que,
pour une rotation totale du stator, il crée n-1 signaux de position ayant la même
largeur de signal et un signal de position ayant une largeur inférieure à celle des
n-1 autres signaux de position ou ayant une largeur nulle, et le moteur comporte en
outre un dispositif (25) de détection de position de référence qui traite logiquement
les signaux de position afin qu'il donne un signal de position de référence correspondant
pratiquement audit signal de position.
8. Moteur autosynchrone à courant continu selon la revendication 7, comprenant en outre
un circuit (22) générateur d'un signal pulsé destiné à former n signaux pulsés à chaque
tour complet du rotor à partir de la force contre-électromotrice créée dans l'un au
moins des bobinages de stator, et dans lequel
le dispositif (25) de détection de position de référence crée un signal de position
de référence par tour du rotor (1) à aimant permanent par traitement logique des n
signaux pulsés provenant du circuit (22) générateur de signaux pulsés, et des n signaux
de position provenant du dispositif (19) de détection de position.
1. Bürstenloser Gleichstrommotor mit einem permanentmagnetischen Rotor (1), der magnetisiert
ist, so daß er 2n Pole aufweist, (wobei n eine positive, ganze Zahl ist) mit mehreren
an einem Stator angebrachten Statorspulen (2a, 2b, 2c), mit einer Spulentreibschaltung
(6) zur Erregung der Statorspulen, mit einem Positionsfühler (19), der zur Wahrnehmung
mindestens einer speziellen Drehlage des Rotors zusammengesetzt ist, mit einer Anlaßschaltung
(16), mit einer dem Positionsfühler zugehörigen Rechnerschaltung (21), um ein die
Drehlage des permanentmagnetischen Rotors (1) angebendes Signal dadurch zu erhalten,
daß eine gegenelektromotorische Kraft verarbeitet wird, die in jeder Statorspule entsteht,
und mit einem Schaltkreis (20) zur Umschaltung zwischen einer Anlaßschaltanordnung
und einer normalen Laufschaltanordnung, dadurch gekennzeichnet, daß die Anlaßschaltung
(16) einen Oszillator (41) zur Erzeugung von einem Pulssignal aufweist, das bei der
Anlaßschaltanordnung der Spulentreibschaltung (6) zugeleitet wird, um die Statorspulen
nacheinander zwangsweise zu erregen, daß der Schaltkreis eine Zustandstreibschaltung
(20) ist, die die Spulentreibschaltung (6) von einer Reaktion auf ein von der Anlaßschaltung
(16) ausgegebenes Signal in der Anlaßschaltanordnung zu einem von dem Positionsfühler
(21) ausgegebenen Signal in der Laufschaltanordnung ausschließlich dann umschaltet,
wenn der Positionsfühler (19) eine Drehlage des Rotors wahrnimmt, die einem die Drehlage
angebenden Signal entspricht, gemäß dem eine speziell vorgegebene Statorspule erregt
werden soll.
2. Ein bürstenloser Gleichstrommotor nach Anspruch 1, wobei die dem Positionsfühler zugehörige
Rechnerschaltung (21) einen Rektifizierungsschaltkreis (3), welcher die Gesamtheit
oder einen Teil des nicht erregten Bereichs von der gegenelektromotorischen Kraft
wegnimmt, einen Stromspannungsumwandlungsschaltkreis (4) vom Entladungstyp, welcher
ein Signal des Rektifizierungsschaltkreises in einen Strom umwandelt, ein Stromspannungsumwandlungsschaltkreis
(5) vom Anziehungstyp, welcher den Ausgangswert des Rektifizierungsschaltkreises in
einen weiteren Strom umwandelt, und einen Integrationskondensator (11) umfaßt, welcher
von dem Stromspannungsumwandlungsschaltkreis (4) vom Entladungstyp und dem Stromspannungsumwandlungsschaltkreis
(5) vom Anziehungstyp geladen und entladen wird.
3. Bürstenloser Gleichstrommotor gemäß Anspruch 1 oder 2, der ferner eine einen Anfangswert
einstellende Schaltung (50) enthält, um beim Anlassen des Motors einen Anfangswert
in die dem Positionsfühler zugehörige Rechnerschaltung (21) einzugeben.
4. Bürstenloser Gleichstrommotor gemäß Anspruch 1, 2 oder 3, bei dem die Anlaßschaltung
(16) einen Sägezahn-Oszillator (41) zur Erzeugung eines Sägezahnsignals, einen Pulssignal-Generator
(42) zur Erzeugung von Pulssignalen aus dem Sägezahnsignal, einen Frequenzteiler (47)
zur Frequenzteilung an den aus dem Pulssignal-Generator (42) kommenden Pulssignalen
und einen Verteiler (43) enthält, um aus den der Frequenzteilung unterzogenen Pulssignalen
verteilte Signale zu erhalten, die der Spulentreibschaltung (6) zugeleitet werden,
um die Statorspulen nacheinander zu erregen.
5. Bürstenloser Gleichstrommotor gemäß einem der vorhergehenden Ansprüche, der ferner
eine einen Treibstrom steuernde Schaltung (48) enthält, um einen Treibstrom zu unterdrücken,
der von der Spulentreibschaltung (6) an die Statorspulen geliefert wird, wenn die
Spulentreibschaltung (6) von einer erregten Spule zu einer anderen überwechselt.
6. Bürstenloser Gleichstrommotor gemäß einem vorhergehenden Anspruch, der ferner eine
anfänglich erregte Phasenwahlschaltung (49) enthält, die beim Anhalten des permanentmagnetischen
Rotors (1) und bei der Wahrnehmung einer speziellen Lage durch den Positionsfühler
(19), bei der eine spezielle Statorspule (2c) unter den Statorspulen (2a, 2b, 2c)
erregt werden soll, die Anlaßschaltung (16) zur Erregung der speziellen Statorspule
einstellt und beim Unterbleiben der Wahrnehmung der speziellen Lage die Anlaßschaltung
(16) derart steuert, daß eine andere Statorspule erregt wird, die sich von der speziellen
Statorspule unterscheidet.
7. Bürstenloser Gleichstrommotor gemäß einem der vorhergehenden Ansprüche, bei dem der
Positionsfühler (19) derart zusammengesetzt ist, daß bei jeder vollständigen Drehung
des Stators n - 1 Positionssignale gleicher Breite, ein Positionssignal von geringerer
Breite als die der n - 1 Positionssignale oder ein Signal ohne Breite entstehen, und
bei dem der Motor ferner einen Bezugspositionsfühler (25) enthält, der die Positionssignale
logisch bearbeitet, um ein Bezugspositionssignal zu erhalten, das im wesentlichen
mit dem einen Positionssignal übereinstimmt.
8. Bürstenloser Gleichstrommotor gemäß Anspruch 7, bei dem ferner eine Pulssignale erzeugende
Schaltung (22) vorgesehen ist, um bei jeder völligen Rotorumdrehung n Pulssignale
aus der elektromotorischen Kraft für den Zähler zu erhalten, die in mindestens einer
Statorspule erzeugt wird, und daß der Bezugspositionsfühler (25) je Umdrehung des
permanentmagnetischen Rotors (1) ein Bezugspositionssignal dadurch erzeugt, daß n
Pulssignale aus der die Pulssignale erzeugenden Schaltung (22) und n Positionssignale
aus dem Positionsfühler (19) logisch bearbeitet werden.